1. Field of the Invention
The present invention relates to a heat-treating apparatus for semiconductor producing equipment, in particular, to a heat-treating apparatus with high sealing characteristics.
2. Description of the Related Art
When semiconductor devices are produced, semiconductor wafers are heat-treatinged by for example oxidation-diffusion process or CVD process.
In a heat-treating apparatus used for such a heat treatment, a cylindrical heater is disposed around a cylindrical reaction vessel which is made of a heat resisting material such as quartz. Around the heater, a cylindrical heat resisting material is disposed. The reaction vessel comprises a gas supply port and a gas exhaust port which are made of quartz glass. The gas supply port is connected to a gas supply portion. The gas exhaust port is connected to a gas exhaust portion. Both the gas supply port and the gas exhaust port are made of quartz glass.
In such a heat-treating apparatus, a semiconductor wafer is disposed inside the reaction vessel in which various heat-treatinges are performed. Examples of process gases are oxygen (O.sub.2), nitrogen (N.sub.2), hydrogen chloride (HCl), hydrogen (H.sub.2), oxychloride phosphorus (POCl.sub.3), and water vapor (H.sub.2 O).
During the heat-treating, while a gas is being exhausted from the reaction vessel, a predetermined process gas is supplied into the reaction vessel which is decompressed to a predetermined pressure or restored to the normal pressure. After the heat-treating is completed, an inert gas such as nitrogen is supplied into the reaction vessel and thereby the process gas is exhausted therefrom.
Although joint portions where the reaction vessel is jointed to the gas supply portion and the gas exhaust portion are heated to around 200.degree. C., however, it should be securely sealed. To securely seal the joint portions, Teflon pipes have been used and tightened. As an alternative method, with quartz pipes or the like and O rings, such joint portions have been sealed.
In the sealing construction of the conventional heat-treating apparatus, an end of a Teflon pipe is connected to a gas supply port integrally constituted on a side wall of the reaction vessel made of highly pure quartz, the other end of the Teflon pipe being connected to a Teflon hose.
However, in the sealing construction of such a heat-treating apparatus, since the Teflon pipe is exposed to high temperature atmosphere for a long time, it is hardened and deformed. Thus, a gas tends to leak from the sealing portions.
In another sealing construction of a heat-treating apparatus, an end of a quartz pipe is tightly connected to a gas supply port integrally constituted on a side wall of a reaction vessel made of highly pure quartz. Examples of O rings are made of fluororubber which can withstand high temperatures of around 200.degree. C. which are merchandized as trade marks of "BAITON", "CALLETS", and so forth.
However, with the sealing construction having such O rings, the elasticity of the O rings will be likely lost due to aged tolerance, thereby deteriorating the sealing characteristics. In addition, the conventional O rings tend to strongly adhere to quartz pipes by heat. Moreover, if a gas leaks from an O ring, it will solidify and adhere to a sealing portion. Thus, it will become difficult to remove the quartz pipe from the gas supply port. When an excessive force is applied to the quartz pipe in order to remove it from the gas supply port, they will be damaged. Furthermore, when the O ring is heated to a high temperature, an impure gas takes place and mixes with the process gas, thereby lowering the yield of semiconductor wafers.